Apparatus and method for constructing graving dry docks



Jan. 4, 1944. F; R HARRIS 2,338,111 APPARATUS AND METHOD FOR cons'rnuc'rme GRAVING DRYDOCKS Filed Jan. 14, 1941 WITNESSES 2 VENTOR 3 Patented Jan. 4, 1944 APPARATUS AND METHOD or:

- KCONSTRUCTING GRAVING DRY DOCKS.

I lirede'ricR. Harris, New York, N. Y}: Application January 14,1941, Serial No. 374,318 V V 3 Claims. (01161-64),

My invention refers to a method and to a'combination of structures whereby the building 'of large gr'aving docks is materially reduced in time and cost and my invention'is' especially useful 'wherehigh' hydrostatic pressure heads" are encountered during the construction period as is the case in very deep dry dock basins situated in water bearing soils.

Withthe increase in draft of modern vessels and the-necessity for'providing overdraft in case of accident, the clearance'jdepthover the sills of gravingdocks has increased greatly and with it the increase in headof ground or sea water to be taken care of during the'construction period.

My invention refers especially to the construction of'graving docks when considerableground water heads are encountered as it provides a method whereby the upwards bottom pressure is localized at the ends of the bottom slab and fully overcome by the entire weight thereof, thus renremovable cofferdam form segments that may be used over and over again for the several side wall' sections which afterwards are cemented together by hydraulic concrete.

Therefore, as my invention involves the use of a combination of old elements by means of which a new and useful result is achieved, I do not only lay claim to the combination shown but also to the several necessary steps of my method of construction as part of my invention.

My present method of side wall construction is especially adaptable for the use in combination with other methods whereby a substantially monolithic tremie concrete bottom is placed in situ upon the bottom of the dock excavation.

In the drawing,

Figure 1 is a fractional plan view of the head end of the dock and shows a portion of the monolithic concrete bottom block, with a reticulated recess pattern on the surface thereof, and one of my preferred removable cofferdams located for the construction of a side wall segment.

Figure 2 is a cross section of the dock basin with two of my preferred cofferdams shown at opposite sides thereof. Reinforcing bracing from two levels is shown removed and a temporary site excavation and 2 represents the tremie concrete bottom slab constructed therein.

The slab'2 is preferably built up of tremie concrete poured inside suitable confining steel partitions which may be attached to a skeleton reinforcing structure, and it is shown continued out past the side walls so that receivingre'cesses 3 may be constructed around a sidewall segment 4. V q

The lower ends of interlocking sheeting or sec;- tional sheet piling-5 engage the recesses 3 which form a reticulated pattern around the' bottom slab 2. or sheet piling 5 interlock and are held-together preferably by outside wales I and braced for pressure by an inside cofferdam bracing '8 that I prefer to make removable so that it maybe used over and over again inthe construction of the side wall sections together with the slideable and interlocking sheeting segments which are withdrawn after the work in the cofferdam is completed and flooded. y

The slideable and interlocking sheeting segments are heldtogether by and secured to the wales l and are adapted to'be guided down along the brace uprights 9 and H] which are parts, of the inside cofferdam bracing 8.

It is to be noted that the ends of the wales I rest on the uprights 9 which are held apart by struts ll of the inside bracing 8.

It is understood that the cofferdams for the inshore or head side wall may be made to conform with the general head outline of the dock, which is shown rectangular but may be trapezoidal, circular or elliptical.

At the entrance end of the clock, which end is not shown on the drawing, I prefer to use segmental cofferdams similar to those used for the general wing construction inside which, after unwatering, I prefer to build a proper gate seat.

My preferred method of construction is as follows:

After the site of the graving dock has been selected, the necessary excavation is undertaken and a layer of gravel fill I4 is usually placed on the bottom.

Necessary piling is driven so that the ends of the piles l5 project some three feet out of the gravel fill and on this foundation the tremie concrete bottom slab 2 is built in place in a conventional manner with the surface recesses 3 provided near the ends and sides thereof.

These recesses usually are channel shaped steel sections.

The inside cofi'erdam reinforcing is preferably I The individual sections 6 of the sheeting bolted together and lowered in place as a unit whereupon the interlocking sheet piling segments are guided down in place around the brace uprights 9 and I and with their lower ends placed into the reticulated recess 3 of the bottom slab 2, are fastened to the skeleton structure or bracing 8, and when the cofferdam is completed, unwatering thereof is undertaken. The Water outside of the cofferdam is indicated by the reference character I 5 in Figure 2.

Dry concrete work is now put in place inside the unwatered cofierdam. The skeleton structure or bracing 8 is made in a number of sections in a vertical direction so that when the concrete has been built up to the lower struts I I, these struts and their longitudinal and diagonal bracing are removed after compensating blocking l2 has been put in place, and so on until the inside bracing is entirely removed and the dry concrete work indicated by the dotted outline i3 is completed and the interlocking cofierdams sheeting 5 is removed.

. v The head and entrance ends are also built in a similar manner.

The side wall segments are cemented together, backfill is put in place against the side walls, the pontoon gate is floated in place, and the dock is ready for operation.

I do not wish to be understood as limiting my claims to the construction combination shown as it is evident that alterations and modifications may be made in the adaptation of my device without departing from the scope and spirit of my invention.

I claim:

1. The method of building a basin dry dock in a. water-bearing soil, characterized by constructing a heavy, bottom, cross slab with reticular recesses around its edge portion, assembling a steel skeleton frame of a size to fit over an area enclosed by one of the recesses of the slab, sinking the frame into position on the top surface of the slab, placing sheet piling around the skeleton frame and by means of said frame guiding the piling downward into the recess thus constructing a cofferdam around the frame with the sheet piling extending into the reticular recess around all sides of the cofferdam, in similar manner successively erecting cofierdams around different areas that are surrounded by the reticular recesses, and consecutively unwatering the margin sections enclosed by the respective cofferdams to allow the building of a wing segment therein.

2. A cofferdam structure for use on a heavy, substantially monolithic tremie concrete bottom slab that has reticular recesses in its top surface around the edge portion of said slab, said cofferdam structure extending along only a portion of the length of an edge of the bottom slab and including sheet piling sides that have lower edges extending into a peripheral portion of said recesses on all sides of the cofferdam structure, said coiferdam structure including a skeleton frame for holding the sheet piling against outside pressure when the inside of the cofierdam is unwatered, said skeleton frame being of a size to fit over an area enclosed by one of the recesses of the slab and including guide means that serve to direct the sheet piling into the recesses when the sheet piling is first lowered into position, and said frame also having detachable parts that can be removed after a side wall section of a dry dock has been built on the bottom slab and within the coiferdam.

3. Means for constructing a basin dry dock in a water-bearing soil on a tremie concrete bottom slab that has a reticulated marginal surface recess therein, said means including a cofferdam comprising panels of interlocking sheet piling secured to horizontal wales, a submerged and'temporary skeleton frame that fits over an area of the bottom slab bounded by a closed pattern of the reticulated recess, said frame including portions on which the sheet piling panels are slidable as guide means for directing the lower'ends of said panels into theperipheral recess, and struts in the skeleton frame connecting the guide portions, said skeleton frame being made in a number of sections in a vertical direction so that different portions along the vertical extent of the bracing can be removed during the building of a side wall within the cofierdam.

FREDERIC R. HARRIS. 

